The regulatory legal norm of procedural default interests was introduced in 1980 in the Civil Procedure Act 1881, in response to a very harmful plight for the creditor and in an inadequate regulatory and jurisprudential context to ensure the indemnity and the right of credit reintegration. Later, the legal norm was inserted with little variation in the Civil Procedure Act 1/2000, and has remained largely unchanged in subsequent procedural reform laws, although the current socio-economic reality is different from what it was at the end of the last century and the legal norm remains incapable to resolve many of the issues that its practical application brings forward. The present study aims, first of all, to delve into the basis of the procedural default and to address it from a current perspective. On the other hand, and from the principles derived from this new paradigm, its legal status is examined, trying to find answers to the problems posed by its implementation. This research is divided into five chapters, in the light of constitutional principles and the guarantees arising from the right to an effective judicial protection. From that perspective, and having examined the role and nature of procedural default, the controversy aroused about how to quantify procedural interests is addressed, which is solved under the new liquidity concept set in the LEC, which resulted in the distinction between the generated procedural interests, while the executive motion is presented, and those accrued during the implementation process. The way to proceed is different for each one of these assumptions and it is analyzed on the basis of the procedural law and the judicial practice, while a proposal is made, which, according to the author, should be contained in a regulation on this matter. An investigation that, moreover, seeks to provide procedural mechanisms to set aside the procedural default during the prosecution of recourses in order to guarantee the right to appeal, and analyzes the impact on the obligation to pay procedural interest that derive from the adjourned extent of the procedure. In this line, the possibilities offered by banking interests, account deposits and judicial consignments are analyzed. Also, the study leads to the finding of the dysfunctional nature of the increase of the ordinary rate of the procedural default in two percentage points. This penalty surcharge was grounded in a particular context moment, but, today, it no longer serves to fulfill the purpose for which it was designed. That is why a proposal to build a theoretical framework is formulated in which the ex lege application of the punitive procedural default percentage rate is not forced. The limited legal and doctrinal development of the subject explains the opportunity of this research but also its practical impact, as it directly affects private economy and, ultimately, global economy.